Power tool

A power tool comprising a power source, a speed change mechanism and a tool bit which is driven via the speed change mechanism by the power source and caused to perform a predetermined operation, wherein:

• the speed change mechanism includes first and second rotating shafts disposed parallel to each other, and first and second gear trains having different gear ratios and each having a combination of a drive gear and a driven gear as one unit which are engaged with each other and transmit torque of the first rotating shaft to the second rotating shaft, wherein a torque transmission path via the first gear train is defined as a first power transmission path and a torque transmission path via the second gear train is defined as a second power transmission path, and further includes a first clutch which allows and interrupts power transmission on the first power transmission path and a second clutch which allows and interrupts power transmission on the second power transmission path,
• the power transmission path is switched between the first and second power transmission paths while the first and second gear trains are held engaged, by shifting of the first and second clutches between the power transmission state and the power transmission interrupted state according to a load applied to the tool bit, and
• the speed change mechanism further includes a switching preventing mechanism which prevents the power transmission path from switching between the first and second power transmission paths by inertia of the tool bit at the time of startup of the power source.

A power tool comprising a power source, a speed change mechanism and a tool bit which is driven via the speed change mechanism by the power source and caused to perform a predetermined operation, wherein:

• the speed change mechanism includes first and second rotating shafts disposed parallel to each other, and first and second gear trains having different gear ratios and each having a combination of a drive gear and a driven gear as one unit which are engaged with each other and transmit torque of the first rotating shaft to the second rotating shaft, wherein a torque transmission path via the first gear train is defined as a first power transmission path and a torque transmission path via the second gear train is defined as a second power transmission path, and further includes a first clutch which allows and interrupts power transmission on the first power transmission path and a second clutch which allows and interrupts power transmission on the second power transmission path,
• the power transmission path is switched between the first and second power transmission paths while the first and second gear trains are held engaged, by shifting of the first and second clutches between the power transmission state and the power transmission interrupted state according to a load applied to the tool bit, and
• the speed change mechanism further includes a switching set value adjusting mechanism which is operated by a user and adjusts a switching set value at which the transmission path is switched between the first power transmission path and the second power transmission path.

A power tool comprising a power source, a speed change mechanism and a tool bit which is driven via the speed change mechanism by the power source and caused to perform a predetermined operation, wherein:

• the speed change mechanism includes first and second rotating shafts disposed parallel to each other, and first and second gear trains having different gear ratios and each having a combination of a drive gear and a driven gear as one unit which are engaged with each other and transmit torque of the first rotating shaft to the second rotating shaft, wherein a torque transmission path via the first gear train is defined as a first power transmission path and a torque transmission path via the second gear train is defined as a second power transmission path, and further includes a first clutch which allows and interrupts power transmission on the first power transmission path and a second clutch which allows and interrupts power transmission on the second power transmission path,
• the power transmission path is switched between the first and second power transmission paths while the first and second gear trains are held engaged, by shifting of the first and second clutches between the power transmission state and the power transmission interrupted state according to a load applied to the tool bit, and
• the speed change mechanism further includes a mode switching mechanism which is operated by a user and switches the transmission mode between a first transmission mode in which a torque transmission path is automatically switched between the first power transmission path and the second power transmission path according to the load applied to the tool bit, and at least one of a second transmission mode in which the first power transmission path is used for torque transmission and a third transmission mode in which the second power transmission path is used for torque transmission.